‘That could work.’ Rosalind had looked thoughtful. ‘But how can we do it without the police interfering? I don’t want them involved until I’m sure. And I definitely don’t want Larch arriving before we’re ready for him. Before we’ve got our confession. He doesn’t know these people like we do. He’ll trample about and ruin everything.’

Rosalind wouldn’t tell them who she thought was responsible, which Posy didn’t like. The idea that she could be trapped in a room with a murderer and not know about it was not exactly relaxing. But then, she supposed she’d been in that position all weekend.

Only this time they were going to do something about it.

‘We do it tonight,’ Posy had replied. ‘Larch must have gone home for the night by now, there’s only one officer stationed at the front door. We get everyone together tonight, away from the entrance hall, and we put an end to this. We can send Larch a message at the last moment, so he won’t have time to stop us.’

After that, it had all come together. Right now, Caro and Rosalind would be leaving notes with tiny blue – non-poisonous – flowers, similar to the ones they’d eaten sugared that first night, under everyone’s doors. Nipping out the back door to pick the flowers while the other two waited in the Snug had been a little terrifying, under the circumstances, but Posy had got away with it.

It was late, but the people they wanted to talk to wouldn’t be sleeping tonight, Posy was sure. And even if they were …

A loud, clanging, crashing noise ran through the house, and Posy smiled. Bang on cue.

She couldn’t hear the conversation that must be going on downstairs, but she could imagine it. The policeman rushing in to find Caro staggering against the gong in the entrance hall, drunkenly apologising as she headed for the stairs. The family, and guests, opening their doors and looking into the hallway to find out what on earth was going on at Aldermere now. Caro slurring her words as she told people not to worry, had a touch too much of the after-dinner brandy, going to her room, everyone should go back to sleep.

And she could picture them shutting their bedroom doors – and finding the envelope waiting for them on the floor with its little blue flower.

By now, they’d know they were invited to a meeting, tonight, in this very room. In less than half an hour’s time.

An ‘I’ve gathered you all here today’, as Caro described it. Rosalind called it a J’accuse, which was pithier.

A reckoning, Posy named it in her head.

And that meant, any moment now …